On any Kindle, when connecting to a Realm, it brings the Kindle's background apps and causes Minecraft to stop connecting to the Realm and causes Minecraft to restart.

This happens on basically every kindle. I have attached a demonstration in which I show two kindles and they both do the same thing at around the same time.

Demonstration: on YouTube (it was too big)

Edit: It appears this happens on all mobile devices iOS and Android too.

This crash happens when it tries to download the resource pack. This does not happen on any pcs or laptops. 
Edit: It appears that this crash is caused by downloading large resource packs while connecting to a realm. It can be mitigated by removing any large resource packs.

Note: It appears this problem also affects any bedrock dedicated servers.